An air bag device is a device for inflating an air bag and restraining an occupant in the case of a collision of a vehicle, and for example one for a driver's seat generally has an inflator, which is a gas generator, an air bag capable of inflating by gas of the inflator, and a receiving part made of a soft resin.
A part or all of the folded air bag is received into the above-mentioned receiving part, and at this time the air bag is folded into a predetermined shape, reforming is carried out to prevent shape-collapsing and then it is put into the receiving part and thereby assembled.
However, the package volume of the air bag differs between immediately after folding and after reforming, particularly, because the cloth of the air bag has no fold habit immediately after folding, the folded air bag rises by the tendency to return from its folded state to its original shape, and when an attempt is made to receive it into fixed dimensions a reaction force arises, consequently there has been the problem that the receiving and assembly work is difficult to carry out.
With respect to this, in JP-A-07132789, strapping the air bag with a band made of a film so as to hold its folded state and breaking this band by means of the deployment pressure of the air bag is disclosed. However, when the band is to be broken by means of the deployment pressure like this it is not easy to perform that breaking smoothly.
It is therefore a first object of the invention to, in an air bag device whose receiving and assembling workability have been improved by holding the folded shape of an air bag by means of a band, make smooth breaking of the band possible.
Also, with an air bag device disclosed in the above-mentioned publication, there are problems of manufacturability such as that it is necessary to wind the band avoiding a bolt part of a retainer for fixing the air bag to the inflator and it is necessary to split open the band when inserting the inflator.
It is therefore a second object of the invention to, in an air bag device whose receiving and assembly workability have been improved by holding the folded shape of an air bag by means of a band, achieve further improvement of assembly workability.
On the other hand, conventionally in air bag devices, suppressing jump-out of the air bag during the initial stage of its deployment and controlling its deployment behavior has been carried out. For example, in JP-A-06206508, disposing a flow regulator inside the air bag for changing the direction of gas flow blasting from the inflator to a direction orthogonal to the jump-out direction toward the occupant and thereby reducing jump-out speed to the occupant direction during the initial stage of the deployment and obtaining good deployment behavior is disclosed. However, when a flow regulator is provided, there has been the problem that the labor of when adjusting the shape and arrangement construction of the flow regulator according to the air bag specifications and inflator output characteristics is great.
With respect to this, the present inventors have discovered that, in an air bag device wherein the folded shape of the air bag is held by the above-mentioned band, by adjusting the breaking strength and so on of this band, it is possible to easily make good the deployment behavior of the air bag.
That is, a third object of the invention is to, in an air bag device whose receiving and assembly workability have been improved by holding the folded shape of an air bag by means of a band, obtain good air bag deployment behavior.